jo049179c_si_003.pdf (1.48 MB)
Room Temperature Preparation of Trifluoroethenylzinc Reagent by Metalation of the Readily Available Halocarbon HFC-134a and an Efficient, Economically Viable Synthesis of 1,2,2-Trifluorostyrenes
journal contribution
posted on 2004-10-15, 00:00 authored by Anilkumar Raghavanpillai, Donald J. BurtonTrifluoroethenylzinc reagent [CF2CFZnX] was generated from the readily available halocarbon
HFC-134a by an in situ metalation−transmetalation procedure at temperatures near to room
temperature (15−20 °C). By systematic standardization of the metalation experiments by
manipulation of solvent, cosolvent, temperature, zinc salt, and the base, the trifluoroethenylzinc
reagent was produced in 73% yield at 20 °C in THF medium. The palladium-catalyzed cross-coupling
reaction of the trifluoroethenylzinc reagent with various aryl iodides was carried out under mild
reaction conditions to produce 1,2,2-trifluorostyrenes in 59−86% isolated yields. The stability of
the intermediate trifluoroethenyllithium reagent was compared at different temperatures and
solvent systems. Experimental evidence for the mono-anion from HFC-134a (CF3CHF-) was obtained
by the trapping of the mono-anion with zinc halide in THF/TMEDA medium. The structure and
complexation of both the mono- and bis-trifluoroethenylzinc reagents with TMEDA and other ligands
are discussed.